Friedrich Björn, Janessa Andrea, Artunc Ferruh, Aicher Wilhelm Karl, Müller Gerhard Anton, Lang Florian, Risler Teut, Alexander Dorothea
Department of Internal Medicine IV, University Hospital Tübingen, Tübingen, Germany.
Cell Physiol Biochem. 2008;22(5-6):465-74. doi: 10.1159/000185495. Epub 2008 Dec 9.
Renal fibrosis is characterized by excessive accumulation of extracellular matrix proteins. Recent findings show that transforming growth factor-beta (TGF-beta) induces a rapid but transient expression of early growth response gene-1 (Egr-1) by skin fibroblasts. The present study aims to define the role of Egr-1 in mineralocorticoid-induced renal fibrosis. Therefore, we transiently transfected immortalized human renal fibroblasts (TK188) with recombinant Egr-1 and analysed the transcription of several pro-fibrotic genes (Coll1A1, Coll1A2, osteopontin, TIMP-1, and CTGF). We also examined Egr-1 expression and the regulation of pro-fibrotic genes in DOCA- (deoxycorticosterone acetate) and TGF-beta-treated renal fibroblasts. Finally, we compared Egr-1 gene expression in DOCA/high salt-induced fibrotic kidneys and untreated mice. Egr-1 transfection of TK188 fibroblasts induced the expression of TIMP-1 and osteopontin mRNA. Similar results were obtained after DOCA-activation of TK188 cells. Stimulation of TK188 with TGF-beta, but not with DOCA, resulted in elevated Coll1A1/Coll1A2 and CTGF levels. Co-stimulation with DOCA and TGF-beta was followed by enhanced Egr-1, Coll1A1, TIMP-1, and CTGF transcription. In conclusion, both DOCA and TGF-beta alone or in combination synergistically induced Egr-1 expression by human renal fibroblasts. DOCA induction of TIMP-1/osteopontin is Egr-1 dependent, whereas TGF-beta appears to induce Coll1A1 and CTGF by an Egr-1 independent pathway. In vivo analyses revealed significantly higher Egr-1 transcript levels in DOCA/high salt-induced fibrotic kidneys compared to untreated mice. Thus, we show for the first time that Egr-1 might participate in DOCA-induced renal fibrosis.
肾纤维化的特征是细胞外基质蛋白过度积累。最近的研究结果表明，转化生长因子-β（TGF-β）可诱导皮肤成纤维细胞快速但短暂地表达早期生长反应基因-1（Egr-1）。本研究旨在确定Egr-1在盐皮质激素诱导的肾纤维化中的作用。因此，我们用重组Egr-1瞬时转染永生化人肾成纤维细胞（TK188），并分析了几种促纤维化基因（Coll1A1、Coll1A2、骨桥蛋白、TIMP-1和CTGF）的转录情况。我们还检测了醋酸脱氧皮质酮（DOCA）和TGF-β处理的肾成纤维细胞中Egr-1的表达以及促纤维化基因的调控。最后，我们比较了DOCA/高盐诱导的纤维化肾脏和未处理小鼠中Egr-1基因的表达。TK188成纤维细胞的Egr-1转染诱导了TIMP-1和骨桥蛋白mRNA的表达。DOCA激活TK188细胞后也获得了类似的结果。用TGF-β刺激TK188细胞，但不用DOCA刺激，会导致Coll1A1/Coll1A2和CTGF水平升高。DOCA和TGF-β共同刺激后，Egr-1、Coll1A1、TIMP-1和CTGF的转录增强。总之，DOCA和TGF-β单独或联合使用均可协同诱导人肾成纤维细胞表达Egr-1。DOCA诱导TIMP-1/骨桥蛋白是Egr-1依赖性的，而TGF-β似乎通过Egr-1非依赖性途径诱导Coll1A1和CTGF。体内分析显示，与未处理的小鼠相比，DOCA/高盐诱导的纤维化肾脏中Egr-1转录水平显著更高。因此，我们首次表明Egr-1可能参与DOCA诱导的肾纤维化。
